Sealing BSP fittings

[VicParticipant @vic]

A friend of mine is a CH boiler engineer and put me on to LS-X which works very well on compression fittings. Far quicker than messing about with tape.

[Trevor WrightParticipant @trevorwright62541]

Going back to the earlier reference of female parallel to male taper, I have found this to work superbly with thread tape on pneumatic and hydraulic fittings – the hydraulic fittings are for high pressure CO2 gas – taking up to 60bar pressure. The taper thread will deform the parallel thread and lock solid without the need for face seals, dowty seals etc. and are easily removed and re-used.

It may seem an odd way to use these fittings but are ideal for my hobby of building fighting robots, aka Robotwars, as ordinary pneumatic fittings will not handle these pressures.

Trev

[AjohnwParticipant @ajohnw51620]

Posted by Hopper on 19/01/2017 05:27:20:

Loctite 567 pipe sealer with Teflon is designed to be low shear strength and therefor easy to remove.

I did not see exactly what your application was but if it is just an air compressor for the workshop etc thread tape will be fine as long as it is kept away from the first turn or so of thread.

Have you actually undone a joint made with it Hopper ?

The problem is a mix of things, I noticed the problem when I changed the pipe tail on the back of the 3 in 1 welder to a male euro coupler. Bit's of tape. Despite it's price they have fitted a mesh fitter into the tail on the welder so shouldn't be a problem but I plug the compressor into other things that wont have that. Ok the filter I have fitted will take those out. I may need to change things round as I have gone the simple way. Euro connector from the argon regulator and flow gauge and also straight from the compressor for cutting.

The problem seems to be that the female part is distorted to make the seal so may not need anything at all but as it's only over a couple of threads it can cut the tape. Also tape about 6mm wide would be easier to use. I had no luck finding any but the tape could still get cut.

I have the la co slick tight now ordered from screwfix before I noticed wickes keep it at the same price. It's a very thick ptfe paste. So thick it might be "interesting" to use but I get the impression that the general idea is to simply wipe any excess off so will try adding a band around the area where the taper meets the female part.

One thing I like about the la co is they haven't gone to any trouble to seal the bottle so if I do any compression fittings in n years time it may well still be ok – Providing it works on those. It's not too good on parallel threads according to wickes but tape is usually fine for those on taps etc.

John

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Edited By Ajohnw on 19/01/2017 13:48:55

[AjohnwParticipant @ajohnw51620]

I tried the slick tight on one joint. It's an amazing lubricant. The female part went on so far I was concerned about something stripping but it still tightened solid eventually.

The brush built into the lid would be more suitable for much larger fittings – say 1" od pipe or more.

The regulator on the compressor is diecast so don't think I will be using it there. I'll stick with tape but cut it to 1/4" wide as that should help and any bits over 20um get trapped by the filter from there anyway.

Don't think I will ever buy any titanium coated drills again. As my metal work gear is rather packed away I used my woodwork ones. Not cheap. To refit the filter in the pipe tail on the welder I had to drill the hole out as the serrated part has been cut off. Brass and even extreme pressure wouldn't cause the drill to cut. The hole was a bit too shallow really and as I had the fitting off I managed to get my hands to my metal work ones – woosh I nearly drilled too far. The drill even grabbed in the brass. I had wondered if it was some sort of bizarre material.

John

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[John Stevenson 1Participant @johnstevenson1]

Posted by Ajohnw on 20/01/2017 22:28:48:

. I'll stick with tape but cut it to 1/4" wide as that should help

John

Do like real engineers do and just fold it double as you wind round.

Simples but if it was harder you would need a new thread, keyboard and armchair.

[AjohnwParticipant @ajohnw51620]

Posted by John Stevenson on 20/01/2017 22:38:50:

Posted by Ajohnw on 20/01/2017 22:28:48:

. I'll stick with tape but cut it to 1/4" wide as that should help

John

Do like real engineers do and just fold it double as you wind round.

Simples but if it was harder you would need a new thread, keyboard and armchair.

Tried John it makes it more difficult otherwise I would have done it that way.

John

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[John Stevenson 1Participant @johnstevenson1]

Well I suppose that's one test that sorts the men out from the boys.

[Gordon WParticipant @gordonw]

May have missed it, but- PTFE tape sold as"suitable for gas " is thicker and generally better. Can be easily folded.

[Bill StarlingParticipant @billstarling10428]

Same question but a different slant. What's the best way to seal a fitting at a particular angle, such as a water gauge fitting, rather than just doing it up tight?

Thanks, Bill.

[Ian PParticipant @ianp]

Posted by Bill Starling on 21/01/2017 09:30:54:

Same question but a different slant. What's the best way to seal a fitting at a particular angle, such as a water gauge fitting, rather than just doing it up tight?

Thanks, Bill.

It seems to me that the most important and guiding aspect is the integrity of the seal rather. Over or under tightening of a joint just so something looks cosmetically right, is bad practice. (but I know it happens)

Same applies to lining up all the slots in adjacent screwheads, surely its not coincidence but they cannot all be tight.

For the gauge problem, use a 'nut and nipple' or compression type fitting.

Ian P

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Ian Phillips on 21/01/2017 09:53:46:

For the gauge problem, use a 'nut and nipple' or compression type fitting.

.

What a great name for a Pub … 'The Nut and Nipple'

MichaelG.

[AjohnwParticipant @ajohnw51620]

Yes the gas spec one is thicker and seems to be usually supplied on a yellow reel. Just 1 1/2 laps should be applied in a left had screw fashion if it's on a right hand thread. Also may be marked high density.

Having used it I think it's an "improvement" we can do without and it still shreds anyway and behaves almost like it's been pre stretched.

You might gather that I have used it and wasn't impressed. I've used the other stuff a number of times and when undone no signs of shredding but different type of joint.

Eihell had used it on the euro coupler supplied loose with the compressor. Their answer was to use the right width and a bit more of it. Result – wont actually go into the female half and finishes up as a sort of ptfe O ring. Not much more either. It might be ok on bigger fittings over 1/4 " bsp. I have seen it used on a cooker hose but it didn't stretch into the threads like usual stuff does.

Parweld use a liquid ptfe. It looks like the screw things in until the taper nearly meets and apply a tiny drop of it. Having undone one I think people would be rather surprised how much effort that took. Maybe the loctite one is better but it's too late to find out once it has been done up.

John

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Edited By Ajohnw on 21/01/2017 10:16:49

[JasonBModerator @jasonb]

Posted by Bill Starling on 21/01/2017 09:30:54:

Same question but a different slant. What's the best way to seal a fitting at a particular angle, such as a water gauge fitting, rather than just doing it up tight?

Thanks, Bill.

Usual practice for models is to use shim washers, all the ME suppliers that sell steam fittings will have these in various thicknesses and diameters, usually soft copper but sometimes aluminium. If you know the tpi of the thread it is easy enough to get an idea of what washer to use eg 40tpi thread wants about a 0.006" washer to make it tight a 1/4 turn sooner than if used without a washer.

[HOWARDTParticipant @howardt]

I have always PTFE tape where required and not had a problem. The tape is applied a couple of threads in on the fitting and only a couple of turns. The tape does not shred until you remove the fitting and then only if the threads are rough, it does remain in the root of the thread most times when the fitting is removed. I would use a liquid sealant on small model fittings at final assembly, the root clearance is obviously a lot less than a standard air fitting which is what the original question was about.

[AjohnwParticipant @ajohnw51620]

Posted by Michael Gilligan on 21/01/2017 10:04:50:

Posted by Ian Phillips on 21/01/2017 09:53:46:

For the gauge problem, use a 'nut and nipple' or compression type fitting.

.

What a great name for a Pub … 'The Nut and Nipple'

MichaelG.

The catalogue I used called them breakable joints. The half with no external nut has a hex hole through it.

It's also possible to get bsp lock nuts.from 1/8" bsp and up where I looked. They have a very comprehensive range of fittings so probably hard to find.

In brass though the start at £0.88 each in 1/8" bsp getting to £1.58 at 1/2" bsp – and £4.75 at 1" bsp. The steel ones are much cheaper.

John

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